U.S. Pat. No. 6,929,974 B1 (Motorola) discloses a microdevice having a hermetically sealed cavity to house a microstructure between the substrate and the cap. The microstructure may be a gyroscope that is mounted on protrusions of the substrate (FIG. 1B of U.S. Pat. No. 6,929,974 B1). Alternatively the microstructure may be an element mounted on the rim of a recess of the substrate (FIG. 6B). The cap has one recess for each microstruture and in each recess there is an embedded crystalline silicon getter layer. The getter layer helps maintain the vacuum within the cavity. In one embodiment, the microdevice comprises a substrate, a cap and an isolation layer. A cavity is at least partially defined by a recess in the cap.
US 2010/0025845 A1 (Fraunhofer Institut) discloses a multiple element component which is to be subsequently individualized by forming elements containing active structures. The component comprises a flat substrate and also a flat cap structure which are bound to each other such that they surround at least one first and one second cavity per component which are sealed against each other and towards the outside. The first of the two cavities is provided with getter material and has—due to the getter material—a different internal pressure than the second cavity.
EP 1 412 550 B1 (Saes Getters) discloses a method for producing MEMS devices with integrated getter. The starting is the problem when using known CVD or sputtering steps for producing localized deposits of gas absorbing materials in the course of known solid state production steps. Obviously, EP 1 412 550 B1 is based on the presumption that localized deposition would imply resin deposition, local sensitization of resin, deposition of gas absorbing material and subsequent removal of sensitized resin and of gas absorbing material, so that the gas absorption material is left in the area from which the resin had been removed. This would increase the complexity of the device production and have the risk of cross-pollution. The goal of EP 1 412 550 B1 is to overcome the problems of the prior art with respect to the complexity of the production process. The surface of the support on which the MEMS devices are constructed has cavities or hollows. Said hollows are designed to form a space for housing mobile structures of the micromechanical devices that protrude from the base. The mobile structures are fixed to the top surface of the bottom part and rise up from said top surface. Therefore, the space provided by the hollow is necessary and sufficient for housing the mobile structure and the mobile structure projects into the space of the hollow and is surrounded by the hollow.
The prior art does not fulfill all needs of modern MEMS technology (MEMS=micro electro-mechanical system).